Joshua Dubnau - US grants

? DESCRIPTION (provided by applicant): The TDP-43 protein plays a role in a broad suite of neurodegenerative disorders including Frontotemporal lobar degeneration (FTLD), amyotrophic lateral sclerosis, and potentially, Alzheimer's disease. TDP-43 is a multifunctional protein with many known cellular roles. So, while the importance of TDP-43 in neurodegeneration is established, the mechanisms of TDP-43 toxicity are unclear. We have discovered a new role for TDP-43 in regulating small-RNA based gene silencing, which is critical to block expression of retrotransposons. Retrotransposons are virus-like sequences that are encoded in our genomes and are capable of replicating and inserting at new chromosomal positions. The toxic potential of transposons in the germline is established. So our discovery provides a plausible hypothesis for toxic effects of TDP-43 in neurons. Our preliminary studies provide strong evidence that TDP-43 normally helps to silence transposons and that this function is disrupted both in FTLD patients and a Drosophila disease model. Our proposed experiments will use genetic manipulations in Drosophila to test three key specific hypotheses: 1) that TDP-43 pathology disrupts argonaute-2 mediated silencing; 2) that TDP-43 pathology activates retrotransposons in Drosophila brain; 3) that Retrotransposon activation contributes to neurodegeneration

DESCRIPTION (provided by applicant): Stimulus valuation is a critical step in determining how we relate with the world. Yet the way the brain computes and represents value remains a matter of much debate. The assessment of potential food sources provides an expedient framework to address value representation in the brain given its ubiquity in nature. Moreover, with the global population facing overwhelming rises in the prevalence of obesity and obesity-related serious medical conditions, the need for understanding the processes governing food selection and preferences has become of paramount importance to human health. Under normal conditions most animals, including Drosophila, are extremely discerning about what food sources to approach, even when given the choice between multiple viable options and odors are one of the most important sensory cues all animals use to track, evaluate and select among available foods. How does the brain represent complex stimuli, in this case odorants, in order to generate appropriate behaviors to environmental cues? Drosophila are an unparalleled model organism with which to study such questions given their complex behavior, relatively tractable nervous system, and the wealth of genetic tools available to both observe and manipulate targeted neural populations. We will first establish Drosophila's partiality for differing food odrs behaviorally. We will then examine with single-cell resolution, using in vivo two-photon calcium imaging, the relationship between observed food- odor values and activity in targeted subsets of olfactory and neuromodulatory neural populations. We are specifically interested in the role of Drosophila Neuropeptide F neurons, the functional homolog of mammalian orexigenic Neuropeptide Y which is a prominent regulator of food-related appetitive behaviors. We will then genetically manipulate neural activity in these populations, both chronically and acutely, to alter behavioral preferences, establishing necessity and sufficiency. Once critical neural subsets are established we will map the connectivity of these neurons using a combination of photoactivation and immunostaining and then determine the functional characteristics of downstream targets through both genetic manipulation and functional imaging. Taken together, these experiments aim to describe how value of a specific class of stimuli, food odor, is flexibly represented in the brain and delineate a neural circuit for such flexible behavior. Our proposal to identify the manner and circuits by which the central brain computes food-odor value will not only inform our understanding of how the brain organizes incoming food-related information but ultimately how the brain translates sensory input into behavioral responses.

PROJECT ABSTRACT Most neurodegenerative disorders exhibit highly heterogeneous genetic underpinnings. For example, with Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD) and Parkinson's disease (PD), mutations in different genes are causal in distinct subsets of families. In addition to this genetic heterogeneity among inherited cases, the majority of individuals exhibit sporadic forms of these disorders in which there are no known causal mutations. In part because of this sporadic onset, it is widely accepted that (largely unknown) environmental forces are at play in the initiation and/or progression of each of the above disorders. This proposal will use a systems approach in Drosophila to identify forces that drive initiation, as well as common cellular responses that may modulate progression. This will be accomplished by three scientific aims. First, we will test a series of cellular stressors, behavioral stressors, and models of injury/inflammation. The effects of these manipulations will be assayed by following 7 different neurodegenerative phenotypes and biomarkers, including a novel assay of endogenous retrovirus replication. Second, we will use a relatively new approach to purify the population of cells that are most impacted, and profile active transcription within the nuclei. This experiment will identify common downstream cellular responses. Finally, we take advantage of high throughput genetic approaches in Drosophila to systematically test for functional impact of identified gene targets.

Project Abstract The Endogenous Retrovirus (ERV) retroelement family comprises approximately 8% of the human genome. Strong evidence is emerging that abnormal de-repression of normally silenced ERV species, including HUMAN ERV-K (HERV-K), plays a role in age-related neurodegenerative disease, including a subset of the ?tauopathy? syndromes and those related to TDP-43 proteinopathy. In addition, there is strong evidence that ERVs and LINE-like retrotransposons are increasingly expressed with age in brain and other tissues. The hypothesis that such repetitive, mobile elements contribute to normal aging and to neurodegeneration is now receiving strong support by a remarkable coalescence of preclinical in vivo work in Drosophila, ex vivo work in mammalian cell culture systems, and postmortem studies in cerebral cortex from human subjects. Unfortunately, to date, there are no mammalian in vivo models to monitor long-term sequels of neuronal ERV expression and replication, including implications for neuronal maintenance and degeneration risk. To provide the field with such type of urgently needed model, we propose a collaborative effort supported by supplemental to a current NIA-sponsored grant (PI Dubnau, RF1AG057338, A systems approach to uncover upstream activators and common downstream pathways of neurodegeneration in a Drosophila model; Project start 09-15-2017, end 06-30-2022) and a current NIMH-sponsored R01 parent grant (PI Akbarian? MH117790-01, Epigenomic Regulation of a Large Neuron-Specific Chromatin Domain, Project start 07-09-2018 , end 05-31-2023). The former is focused on neurodegeneration in a fly model including impact of retrotransposons and ERVs. The latter on the regulation of the spatially organized neuronal genome in mice with conditional deletion of Kmt1e/Setdb1, a histone methyltransferase for the repressive histone mark, methyl-H3K9.